FR2572816A1 - ELECTROMAGNETIC SERVICE DEVICE - Google Patents

Abstract

THE ELECTROMAGNETIC SLAPPING DEVICE OF THE INVENTION INCLUDES A DRIVE CONTROL CIRCUIT 100 AGENCY TO PRODUCE, FOR AN ELECTRIC MOTOR 20, AN AUXILIARY TORQUE TO BE APPLIED TO AN OUTPUT SHAFT, TO PRODUCE A GO CONTROL SIGNAL USED TO PROVIDE AN ARMATURE CURRENT IO IN QUANTITY SET TO THE MOTOR, IN A REGULATED DIRECTION OF CONDUCTION OF THIS CURRENT, AS A FUNCTION OF A DETECTION SIGNAL VR, V1 FROM A DETECTION MECHANISM 13 SERVING TO DETECT A PHASE BETWEEN A D SHAFT 'INPUT AND OUTPUT SHAFT. THE ROTATION SPEED OF THE ELECTRIC MOTOR 20 IS SET BY MEANS OF THE VA CONTROL SIGNAL, BEING PROPORTIONAL TO THE QUANTITY OF THE PHASING. APPLICATION TO ELECTRIC SERVODIRECTION SYSTEMS FOR VEHICLES.

Description

2572 8 1 6

  ELECTROMAGNETIC SERVICE DEVICE

  The present invention generally relates to a

  electromagnetic servo device. More specifically

  The invention relates to an electronic servocontrol device

  a type suitable for use in a service system.

  electric vehicle type steering system.

  In view of the problems posed in the servodrive systems,

  Because of the fact that their structure is complicated, in recent years a variety of electric-type power steering systems for vehicles have been proposed. In these power steering systems of the electric type

  different types of electronic servo device have been used.

  tromagnétique. For example, in Japanese Patent Application No. 59170812,

  filed on August 16, 1984, the present Applicant has proposed a

  positive electromagnetic servo-control for

  electric power steering for vehicles.

  This electromagnetic servocontrol device included an input shaft arranged to be actively connected to a steering wheel

  of direction, an output shaft arranged to be connected active-

  a bearing wheel to be rotated, the output shaft being coaxial with the input shaft, a torque sensing mechanism actively connected to both the input shaft and the drive shaft. output, an electric motor placed to rotate around the output shaft, coaxially with it, for him

  provide an auxiliary torque, and a drive control circuit

  arranged to control the drive of the electric motor con-

  to a group of detection signals of the detection mechanism

couple.

  The torque sensing mechanism was arranged to generate

  derive a pair of signals as its detection signals represent

  both the degree as well as the direction of an angular difference

  lative according to the circumference produced on the input shaft by

  relationship to the output shaft when a management couple was

  the input shaft, these signals were supplied to the drive control circuit, in which they were processed for

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  producing a torque magnitude signal and a torque direction signal for sending to the electric motor an armature current in an amount dependent on the torque magnitude signal in each of its conduction directions as a function of the torque direction signal, the output shaft thus receiving the auxiliary torque,

  while an electromagnetic torque produced in the electric motor

  was transmitted as an auxiliary torque to the output shaft

  via a speed reduction mechanism.

  As a result, the armature current to be supplied to the electric motor increased in quantity, when the relative angular difference along the circumference between the input and output shafts

  output was increased with a management torque applied to the

entrance.

  Moreover, in this electronic servocontrol device

  Magnetic, the torque magnitude signal had a dead zone

controllable to adjust.

  Therefore, in this electronic servo device

  magnet, the torque produced in the electric motor was trans-

  put as an auxiliary torque to the output shaft through the speed reduction mechanism in a smooth or regular manner, which suitably reduced, for a driver of the vehicle, the load he or she would otherwise have had to wear while operating

  the steering wheel, providing characteristics of di-

favorable reaction.

  However, in this electromagnetic servo device

  As well as in other conventional devices for electric power steering systems for vehicles, there has been a need to achieve a result, such as rotating an output shaft with good sensitivity, relative to the rotation of the vehicle. a tree

  input or, more particularly, at its speed of rotation.

  The present invention has succeeded in achieving this result

  in a conventional electromagnetic servo device.

  Accordingly, an object of the present invention is to provide

  an electromagnetic servo device, in which a

  output shaft has the ability to rotate with good sensi-

  the speed of rotation of an input shaft.

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  To achieve this object, the present invention provides, in an electromagnetic servo device including an input shaft, an output shaft, an electric motor for producing a

  auxiliary torque to be applied to the output shaft, a means of

  detecting a phase difference between the input shaft and the output shaft, and a control circuit arranged to provide a control signal, for the electric motor, thereby to provide a controlled quantity of armature current, a controlled conduction direction thereof, as a function of a detection signal from the detection means, an improvement constituted by the control circuit in which the control signal for the motor is provided to adjust a rotation speed of the motor according to the

detection signal.

  Other features and advantages of the present invention

  will be highlighted in the following description, given in

  As a nonlimiting example, with reference to the accompanying drawings in which: Figure 1 is a detailed block diagram of a circuit

  driving control of an electronic servocontrol device

  tromaonetic according to a preferred embodiment of the present invention, when arranged for use in an electric power steering system for vehicles; Figures 2A to 2D are diagrams representing

  characteristic curves of the output signals of some of the

  main circuit elements contained in the drive control circuit of Figure 1, respectively; Fig. 3 is a block diagram of the drive control circuit of Fig. 1; Figure 4 is a longitudinal sectional view of a servo unit of the electromagnetic servo device, which is controlled by the drive control circuit; Figure 5A is a sectional view, showing part of

  of a mechanism for detecting an angular displacement

  relative lag as a phase shift between an input shaft and an ar-

  output of the servo unit, along a line 5A-5A of Figure 4; and Figures 5B and 5C are top and side views showing a moving member for detecting displacement.

  angle of the mechanism of Figure 5A, respectively.

  In FIGS. 1 and 3, reference numeral 100 indicates the assembly of a drive control circuit of an electromagnetic servocontrol device according to an exemplary embodiment.

  preferred embodiment of the present invention, when mounted in a system

  electric power steering system of a vehicle (not shown).

  Figures 2A to 2D show characteristic curves of some of the signals which will be described in the following to extract

  of essential circuit elements of the driver control circuit

  100. The structure of the electromagnetic servo-control device

  The tick is shown in Figures 4 and 5A to 5C, which are

  sectional views of the whole and an essential part, respectively

  of an electromagnetic servo unit 200 consti-

  killing the electromagnetic servocontrol device, the servo unit 200 being controlled by the control circuit

  100, this unit 200 having been developed initially

  by the present Applicant and having a mechanical structure similar to that defined in the Japanese patent application

No. 59-170812 mentioned above.

  To facilitate understanding, the mechanical structure of the electromagnetic servo unit will first be described with reference to FIGS. 4 and 5A to 5C, before entering the

  description of the constitution and the function of the circuit

driving control 100.

  FIG. 4 represents the sectional view as described and, more particularly, a sectional longitudinal sectional view of

  quarter of the electromagnetic servo unit 200.

  The servo unit 200 comprises an input shaft 1 supported to rotate by a ball bearing 2 as well as by a needle bearing 3 and connected at its axially outer end to a steering wheel (not shown) of the control system. power steering, and an output shaft 4 arranged coaxially with the input shaft 1 and interconnected by means of a bar

  torsion 8 with the input shaft 1. The output shaft 4 is also

  It is supported to rotate by a ball bearing 5 and by needle bearings 6, 7. The output shaft 4 comprises at its

  outer end axially a fluted portion 4a mounted ac-

  in a steering box (not shown) of the rack and pinion type of the power steering system. As will be described later, an end portion

  inner axially and uniquely formed lb of the shaft of

  1 is engaged by its innermost end in an axially axially and uniquely formed end portion 4b of the output shaft 4, where it is supported to rotate, the

  needle bearing 3 being placed therebetween.

  The torsion bar 8 is fixed by its end 8a inserted

  in an axial hole 4c of the output shaft 4, to the output shaft

  4 by means of a key 11 and, by its other end 8b inserted into an axial hole 1c of the input shaft 1 and by means of a screw 9, to the input shaft 1 which is thus adapted to have,

  whereas no management couple acts on him, an

  predetermined gullar about its axis relative to the

exit 4.

  In the previous provision, the management couple

  from the steering wheel is applied to the input shaft 1, and

  it is transmitted from it to the output shaft 4 through the medium of

  re of the torsion bar 8, resulting in torsional deformations in the torsion bar 8, thus having a difference

  angle of rotation relative to the circumference, that is to say

  say, relative angular displacement as phase shift produced on

  the input shaft 1 with respect to the output shaft 4.

  On the other hand, in Figure 4, reference numeral 12

  indicates an enveloping direction column used to house the

entry 1.

  The servo unit 200 has, in its axial position o the inner end portion lb of the input shaft 1 is

  engaged in the inner end portion 4b of the output shaft

  4, a relative rotation angle detection mechanism 13 arranged to extend around it and arranged to detect the relative angular displacement produced between the input shaft 1 and the output shaft 4. The detection mechanism 13 consists of a differential transformer 14 fixed to the inner periphery of the steering column 12, and a tubular movable member 15 which is a laminated iron core axially axially fixed around the nested portions 1b, 4b input and output shafts 1.4. The differential transformer 14 has a pair of output terminals connected to the drive control circuit 100, which is

  partially arranged to electrically detect the

  relative angle between the input and output shafts 1,4, then

  that the drive control circuit 100 has a function of

  to supply an armature current Io (FIG. 1) in

  in each controlled conduction direction thereof, to an electric motor 20 to be described hereinafter, which drives the motor 20 according to the magnitude and the direction or direction

  action of the auxiliary torque to extract from it.

  As shown in FIG. 5A, the movable member 15 is in compliance with FIG.

  tact with the input shaft 1 by means of a pair of keyways

  16, 16 fixed to the input shaft 1, and with the output shaft 4 by means of another pair of radial wedges 17, 17 fixed to the output shaft 4, the radial wedges 17, 17 each being spaced peripherally and respectively from a phase shift of 90

  of one of the keys 16,16. For the contact with the cla

  radial vanes 16,16 protruding from the input shaft 1, the movable member

  15 has a pair of contact holes 15b formed therein

  ci to corresponding positions of the periphery so as to

  extend in the axial direction of the torsion bar 8. Egale-

  for contact with the radial wedges17,17 de-

  passing from the output shaft 4, the movable member 15 has a pair of contact holes 15a formed therein which extend

  at an oblique angle to the axial direction of the bar

  torsion 8. The movable member 15 is normally deflected into the

  axial direction, to the left in Figure 4, by means of a

  spiral spell 18 compressed so that it is interposed between this

  15 and the ball bearing 2 mentioned above.

  In the preceding arrangement, between each of the radial keys 17 and the corresponding hole of the elongate holes 15a is

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  left a space due to the precision of the execution. However, on each side 15c serving as machining side of the hole 15a, any game

  due to this space left between the key 17 and the hole 15a is es-

  eliminated by the presence of the spring 18 which normally pushes

  malement key 17 so that it comes into contact with the machining side 15c, while the other side 15d of the hole 15a comprises

  a corresponding game L left against the key 17.

  According to the preceding arrangement, when the input shaft 1 is forced to rotate by a torque applied

  at the steering wheel, which transmits a torque to the output shaft

  4 through the torsion bar 8, a relativeperipheral angular difference is produced, i.e.

  angular displacement between the input and output shafts

  1.4, which axially displaces the movable member 15 towards the right

  te or the left in Figure 4, depending on the direction of rotation

  as well as the absolute value of the angular difference that the

  1 is then forced to undergo with respect to the output shaft 4. The relative angular displacement can thus be detected

  by electrically detecting the extent of the axial displacement of the

  mobile unit 15 by means of the differential transformer 14.

  As shown in Figure 4, the servo unit 200

  comprises a cylindrical casing 19 for accommodating the electric motor

  mentioned above which is arranged coaxially around the output shaft 4. The electric motor 20 is constituted as

  a DC motor having a pair of magnets 21 ser-

  inductor which are attached to the inner periphery of the car-

  ter 19, and a rotor 26 serving as an armature consisting of a tubular shaft

  23 which is supported to be rotated by the bearings

  with needle 6,7 and a ball bearing 22, and a core of

  24 which is attached to the tubular shaft 23 and which is provided with an armature winding 25 arranged to cut, when it is rotating, the lines of the magnetic field produced by the magnets 21. rotor 26 is provided at its left end with a slip ring assembly 27, to which the armature winding 25 is connected by its terminals 25a so as to allow the armature current Io in the necessary quantity to pass through it in each sense of conduction as it should. At each of the necessary electrical angular positions, a broom 29 is brought into contact with

  the slip ring assembly 27, while being pushed normal-

  against the latter by means of a helical spring 28. Through the brush 29, the armature current Io as adjusted is sent from the drive control circuit 100 in the armature winding 25. previous provision, with the applied torque of the steering wheel to the input shaft 1, while the input and output shafts 1, 4 have a relative angular displacement which is produced between them to be detected by the detection mechanism

  relative rotation angle 13, the drive control circuit

  it is necessary to operate to send the armature current

  Io to the armature winding 25, which drives the electric motor

  than 20, so that the rotor 26 rotates around the output shaft 4, independently of it, in the same direction of rotation as

the input shaft 1.

  The rotation of the rotor 24 is transmitted to the output shaft

  4, by means of a speed reducing mechanism constituting

  killed by primary and secondary planet gears 32,33, in which its speed is reduced and the torque increased. In the

  gear reduction mechanism consisting of the two gear stages

  Planetary Swims 32, 33, the primary stage 32 consists of a

  primary solar gear 30 formed along the outer periphery

  the left end portion of the tubular shaft 23 serving as a primary input member, a ring gear or

  toothed crown 31 common attached to the inner periphery of the car-

  ter 19, and three primary planet gears 32a interengre-

  born between the solar and annular gears 30,31. The primary planet gears 32a are supported for pivoting by a disk-shaped flange 32b attached to a secondary input member loosely fitted to the output shaft 4, which member has on it

  a secondary sun gear 33a. On the other hand, the second floor

  re 33 consists of the secondary sun gear 33a, the

  annular graining 31, and three secondary planetary gears

  33b interengaged between the solar and annular gears 33a, 31.

  The secondary planet gears 33b are supported for

  vote by a disk-shaped flange 33c which is attached integrally

  1 to a tubular member 33e, this member 33e being fluted on a portion of the splined portion 4a of the output shaft 4 and further being fixed by a radial bolt 33d also

to the output shaft 4.

  Consequently, when a steering torque is applied to the input shaft 1, the output shaft 4 receives, in addition to the torque at

  transmit to it from the input shaft 1 through the

  the torsion bar 8, an additional torque produced by the electromagnetic actions of the electric motor 20 disposed around the output shaft 4 and transmitted by the speed reduction mechanism, an auxiliary torque being thus applied to the output shaft 4. As a result, in the servo unit 200, a torque applied to the input shaft 1 is apparently amplified when it is transmitted to be applied as an output torque to the output shaft 4 and, therefore, the servo unit 200 has the ability to function as an electromagnetic force amplification device for power steering systems.

of electric type.

  In addition, it will be seen from Figure 5A that, when

  the relative angular displacement as a phase shift between

  input and output 1.4 is increased to a predefined angle

  finished (about 100 in this embodiment), the peripherally moving side faces 1c of the axially inner end portion 1b of the input shaft 1 are brought into contact,

  to be blocked, with the corresponding faces of the lateral faces

  4c of the axially inner end portion 4b of the output shaft 4. In other words,

  with this blocking structure between the input and output shafts

  1.4, the electromagnetic servo unit 200 comprises

  internally a db security mechanism.

  In addition, in the servo unit 200, the torsion bar 8 is arranged to serve partially, while no

  steering torque is applied to the input shaft 1,

  stably anchoring the input shaft 1 to its neutral position relative to the output shaft 4 and, in addition, in part, when a steering torque is transmitted from the steering wheel to the input shaft 1, so that a suitable reaction torque is applied through the input shaft 1 at the end of the steering wheel.

  The constitution and function will be described below.

  tion of the drive control circuit 100 arranged to control

  the action of the electromagnetic servocontrol unit 200.

  As shown schematically in FIG. 3, the control circuit 100 consists of a relative angle detection circuit 71 serving as a phase shift detector for electrically detecting the angle of rotation of the input shaft 1 with respect to the tree of

  output 4, and a motor drive circuit 72 for driving

  The detection circuit 71 and the drive circuit 72 receive a supply voltage of a battery serving as a supply voltage source 75.

  via a main switch 73 and a fuse 74.

  The differential transformer 14 of the angle detection mechanism

  relative rotation 13 receives at the entrance of its primary winding

  re 14a an alternating current signal of a predetermined frequency

  of the detection circuit 71, and generates at the output of its two windings

  secondary elements 14b, 14c, two detection signals Vr, Ve. These signals Vr, Vu are sent to the input of the detection circuit 71,

  in which they are treated to be generated in output direc-

  driving circuit 72 in the form of a combination

  a voltage signal VP representing the angular displacement

  lative as phase shift dP between the input and output shafts 1,4, and two logic voltage signals VR, VL representing the direction of rotation of the input shaft 1 relative to the output shaft 4, this combination of the signals VP, VR, VL being sent to the input of the

  driving circuit 72 for use in driving the electric motor

in accordance with these.

  The detection circuit 71 and the drive circuit 72

  will be described in detail below with reference to Figure 1.

  The differential transformer 14 of the detection mechanism 13 receives, as described, by its primary winding 14a

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  the alternating current electric signal of predetermined frequency of an oscillator 70 contained in the detection circuit 71, and its secondary windings 14b, 14c are arranged to output the detection signals Vr, VE as a pair of voltage signals in alternating current whose amplitude varies differentially as a function of the axial displacement of the movable member of the transformer 14. The detection signals Vr, Vt are first rectified by a pair of rectifiers 34a, 34b and filtered by a pair of low-pass filters 35a, 35b, to be provided as a pair of DC voltage signals Vrl, Vtl respectively to

a pair of subtractors 36, 37.

  Moreover, in the preceding provision, the

  bile 15 is arranged to take, in FIG. 3, its neutral position

  Xo when the relative angular displacement between the input and output shafts 1.4 is zero and no torque steering is applied to the input shaft 1. In addition; it is arranged to move, in Figure 3, in the direction of + X when the tree

  1 as seen from the side of the steering wheel is

  born to the right with respect to the output shaft4 with a clockwise torque applied to the input shaft 1, and, conversely, in the -X direction when the output shaft 1 is turned to the left with respect to the output shaft 4 with a torque acting in the opposite direction of the needles of a

  watch applied to the input shaft 1.

  The voltage signals Vrl, Vel at the output of the filters pass

  35a, 35b are adjusted to have a differentially varying level in accordance with the axial displacement of the movable member, i.e., its vertical displacement in FIG. so at a predetermined voltage level when

  the member 15 is placed in the neutral position Xo.

  In particular, the transformer connection differs

  14 and the circuit structure mentioned above of the detection circuit 71 are such that, when the movable member 15 is caused to move upwards in FIG. 1, while the input shaft 1 is rotated clockwise with respect to the output shaft 4, the signal voltage Vrl increases from the predetermined level proportionally

  the upward movement of the organ 15 while that of the

  General Vil decreases and, on the contrary, when the organ 15 is brought

  to move downwards in Figure 1, while the tree of

  1 is turned counterclockwise relative to the output shaft 4, the first signal Vrl decreases and the last signal Vel increases proportionally to the displacement.

down.

  The voltage signal Vrl from the low-pass filter 35a is directed to both an input terminal plus of the subtractor 36 and a minus input terminal of the subtracter 37, and the voltage signal Vel from the low-pass filter 35b is directed to the

  an input terminal minus the first subtractor 36 and a terminal

  no more input of the last subtractor 37.

  Subtractors 36, 37 are arranged to output a pair of voltage signals Vr2, Ve2, respectively,

  such that Vr2 = Vrl - Vtl and Vf2 = Vtl - Vri.

* In this respect, in the control circuit 100 receiving a

  voltage of the supply voltage source 75 of positive po- larity, even in the case where Vrl <V1, for example, the signal Vr2 in

  output of the subtractor 36 has a voltage that is not allowed

  to become negative, whereas in this case it is noticeably

  sin of zero on the positive side. This characteristic is analogous

  for the voltage signal Vh2 from the subtractor 37,

is lying.

  Therefore, in the previous circuit arrangement, in the case where the movable member 15 is placed in the neutral position Xo, the voltages of the signals Vr2, V42 from the subtracters 36, 37

  both are rendered substantially zero.

  The output signals Vr2, VU2 of the subtracters 36, 37 are each respectively input at the same time as a circuit OR

  38 and a pair of voltage comparators 39,40.

  In the OR circuit 38, the input signals Vr2, V-2 are summed logically to obtain a sighal - representing a relative angular difference or phase shift as an output signal VP

  to be generated at the output in the direction of the drive circuit 72.

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  On the other hand, in one of the voltage comparators 39,40, that is to say the comparator 39, a signal representing a relative direction of rotation or a direction of phase shift as a logic signal VR is obtained at its output. to generate, so that the signal VR has its voltage which is set to a "high" level when the signal of

  Vr2 is higher in level than the input signal V2 and

  calf "low" when the first signal Vr2 is equal to or less than the last signal V42 and, in the other comparator 40, another signal is obtained representing the relative direction of rotation or the phase shift direction, as a logic signal VL to be generated at its output, so that the signal VL has its voltage set to a "high" level when the input signal Vt2 is higher in level than the input signal Vr2 and at a "low" level when the first signal V42 is equal to or less than the last signal Vr2. The logical signals VR, VL are

  also sent to the drive circuit 72.

  In the previous circuit arrangement, the signal VP

  is a DC voltage signal as a signal of dif-

  angular degree of a level which is proportional to the angle of relative angular displacement between the input and output shafts 1,4, and it can therefore be used to know this angle. Else

  On the other hand, the signals VR, VL are a pair of logic voltage signals.

  As rotational direction signals representing the direction of angular displacement of the input shaft 1 relative to the output shaft 4, it is possible to know this direction from them. For example, when it is set to the "high" level, the direction of rotation signal VR implies that the input shaft 1 is rotated clockwise with respect to the output shaft 4, while the direction of rotation signal VL is then set to the "low" level. In contrast, the VL signal as set at the "high" level implies that the input shaft 1 is rotated counterclockwise with respect to the output shaft.

  output 4, while the signal VR is then set to the "low" level.

  The signals VP and VR, V1 have characteristic curves inclined and staggered as shown in FIGS.

2A and 2B, 2C, respectively.

  As shown in Figure 2A, the difference signal

  angular VP has its limit greater than a voltage level Vc corre-

  laying at a relative angular displacement between the input and output shafts 1,4 as increased to the predetermined phase shift, o the safety mechanism constituted by the axially respective inner end portions lb, 4b of the shafts 1, 4 is put into service.

  The driving circuit will be described in detail below.

  72, again referring to Figure 1.

  The voltage signal VP having a variable level proportion-

  the relative angular difference dP is sent to an input terminal more than a differential amplifier 41, and the signals

  logic VR, VL set to "high" or "low" voltage level depending on

  relative direction of rotation are both sent to one

  switching circuit 42 which will be described in the following. In the

  41, the signal VP is processed in a manner which will be

  hereinafter written to produce a voltage signal VP1 which is sent from the output to an input terminal more than one comparator of

  voltages 43, in which it is compared to a pulsed signal in teeth

  saw-saw Vt sent to a lower input terminal of the comparator 43 from a sawtooth wave generator 44, which allows

  to obtain a rectangular pulsed signal VP2 at the output of the comparator

  43 to the switching circuit 42.

  The rectangular pulsed signal VP2 obtained at the output of the com-

  parator 43 by comparing the voltage of the input signal VP1

  to that of the pulsed sawtooth signal Vt is given as a

  voltage signal having a source level Vcc when the signal VP1 is higher in level with the signal Vt, so that, as in the example shown in FIG. 2D, a pulsed signal having a frequency synchronized with the signal VP2 is obtained as signal VP2. sawtooth pulsed signal Vt and a variable pulse width W1 proportional to the voltage level of the output signal VP1 of the amplifier 41. Accordingly, as will be appreciated from

  Figure 2D, the pulsed signal VP2 as output signal of the compa-

  The controller 43 has an average voltage VM1, such that VM1 = Vcc x (W1 / Wo), where Wo is the pulse duration of the rectangular pulsed signal VP2 synchronized with the sawtooth pulse signal Vt. Voltage

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  mean VM1 of the VP2 signal is proportional to the voltage level

signal VP1, as it should be.

  The switching circuit 42 mentioned above is arranged to control the terminal polarity of the electric motor, when a controlled drive signal is applied thereto whose average voltage varies in correspondence with the average voltage VM1.

as will be described below.

  The switching circuit 42 generates signals

  regulated voltage, which will be described in the following, by four

  42a, 42b, 42c, 42d thereof which are connected to the bases of four transistors npn 45,46,47,48 respectively constituting four

  bridge sides of a bridge circuit 49. The bridge circuit 49 is con-

  staged as a polarity determination switching circuit

  in which transistors 42a to 42d are used as its

  switching elements, in which the bridge sides of the transistors 47 have a common terminal 50 to be connected as a side terminal.

  power supply to a positive terminal of the power supply voltage source.

  75 (Figure 3) and in which the bridge sides of the tran-

  In addition, the sistors 46, 48 have a common terminal 51 to be connected as

  from the mass side to ground via a resistor

  52 of resistance value Ra. Common terminals 53,54 are also

  provided between the sides of the transistors 45, 46 and between the sides of the transistors 47, 48, respectively, which are connected,

  as a pair of polarity reversal output terminals in accordance with

  to the conductive-locked states of transistors 45 to 48, brushes 29, 29 of the electric motor 20, respectively. Otherwise,

  in the circuit 49, the bridge sides of the transistors 45 to 48 comprise

  each respectively carry one of four diodes 55

  parallel to the latter, between the collector and the emitter of this transistor, to prevent a reversal of the direction of passage of the

  electrical current of direction set.

  In the previous circuit arrangement, the circuit of

  switch 42 is arranged to drive the pulsed rectangular signal.

  VP2 to the bases of the transistors 45, 48 when the signal

  VR is at the "high" level and the logic signal VL at the "low" level, and, conversely, at those of the transistors 46, 47 when the first signal VR is at the "low" level and the last signal VL at the "level". "high," while the VR, VL signals are controlled to be

  set at the "high" level in an exclusive way.

  For example, when the logic signal VR representing the direction of rotation is set to the "high" level, the reciprocal pulse signal VP2 from the comparator 43 is sent to the bases of the transistors 45, 48, making them conductive, so that a voltage Va is applied to the electric motor 20 with a corresponding polarity, by sending the armature current Io in the direction A indicated in FIG. 1, which drives the rotor 26 of the motor 20

  so that it turns to the right according to the direction of rota-

  input shaft 1 with respect to the output shaft 4.

  On the other hand, when the logic signal VL is set to the "high" level, the pulsed signal VP2 is sent to the bases of the transistors 46, 47 by making them conductive, so that the voltage Va is applied to the electric motor 20 with a corresponding polarity. by sending the armature current Io in the direction B indicated in FIG. 1, which drives the rotor 26 of the motor 20 so that

  - turn to the left according to the direction of rotation

lative.

  As a result, the voltage Va applied to the motor-electric

  that 20 has an effective value corresponding to the average voltage VM1

rectangular pulsed signal VP2.

  With regard to the electric motor 20, which is

  When the voltage Va is applied to send it the armature current Io, it will be easily understood that, if the load imposed as a torque by the output shaft 4 on the motor 20 is constant, the rotation speed N expressed in the number of revolutions per unit of time (hereinafter referred to as "rpm,") is fundamentally proportional to the level of the rms value of the voltage Va, while the rms value of the induced current Io is determined from the torque charge in a unique way. The speed of

  rotation N expressed in rpm of the electric motor 20 is thus

  can be controlled by adjusting the level of the rms value of the voltage Va.

  As shown in FIG. 1, terminal 53 has a voltage which is, for example, its potential relative to ground, this voltage

257 2 8 16

  being applied to be introduced as a voltage signal Var

  at an input terminal more than a subtractor 57 and at a terminal of

  less than another subtractor 58 via a

  Low-pass 56, while terminal 54 also has a voltage which is its potential, which is applied to be introduced as the voltage signal Va. to an input terminal minus the subtractor 57 and to an input terminal plus of the subtractor 58 via another low-pass filter 59. The subtracters 57, 58 output a pair of voltage signals Var ', Vaú', respectively,

  which are sent as input to a circuit OR 60, where they are added

  born logically to obtain a voltage signal Va 'at the output,

  as the signal representing the absolute value of the difference in

  in the electric motor 20, which is sent to an electrical terminal 20

  more than one other subtractor 61, which receives

  at least one signal Vm 'representing the armature current which is a voltage signal at the output of a DC amplifier 63. The amplifier 63 receives at its input a DC voltage signal Vm obtained in putting the tension

  of the ground side terminal 51 of the bridge circuit 49, as a potential

  tiel with respect to the mass at a positive terminal of the resistor

  52, via a low-pass filter 62.

  In the previous circuit arrangement, the signal Va 'sent to the input terminal plus of the subtracter 61 has a voltage level corresponding to the rms value of the voltage Va in the electric motor 20, and, on the other hand, the signal Vm 'sent to the

  input terminal minus the subtractor 61 has a voltage level cor-

  corresponding to the potential at the positive terminal of the resistor 52, this potential being in correspondence with the rms value of the armature current Io. As a result, by giving the DC amplifier 63 an appropriate amplification coefficient, one

  adapts the subtractor 61 so that it has on its side output a

  a reaction voltage signal Vf corresponding to a counter-electric force

  tromotrice produced in the electric motor 20 according to the load torque applied thereto. In this respect, the level of the voltage signal Vf to be generated at the output of the subtractor 61 is

  proportional to the speed of rotation N of the electric motor 20.

2572 8 16

  As shown in Figure 1, the output signal Vf of

  subtracter 61 is sent to an input terminal minus the amplifi-

  Differential Calculator 41 mentioned above, which in turn

  at output the voltage signal VP1 at a variable level proportion-

  the difference between the voltage signal VP whose level is proportional to the relative angular difference dP, and the signal

  Vf, the level of which is proportional to the speed of rotation.

  Nation N of the electric motor 20. The signal VP1 is then sent to the input of the comparator 43, in which it is processed to obtain the rectangular pulsed signal VP2, which is used in the circuit

  switching circuit 42 for driving the electric motor 20 in each

  that desired direction of rotation of it, as described. As a result, the output shaft 4 is arranged to be rotated by the electric motor 20 at a proportionally variable speed.

  the relative angular difference dP as a phase shift between

entrance and exit 1.4.

  The reaction voltage signal Vf to be sent to the input terminal minus of the differential amplifier 41 will be described below. The signals Var ', Va' at the output of the subtractors 57, 58 are given as voltage signals. , such that: Var '= Al x (Var - Vat); and Va - = A1 x (Vat - Var), where A1 is an amplification coefficient, such that the coefficient A1 becomes essentially zero at the positive side if Var (Val in the subtractor '57 and if Var> Val in the subtractor 58,

  as in the case of the subtractors 36, 37 mentioned above.

  The output signal Va 'of the OR circuit 60 is the result of

  the logical sum of the signals above Var ', Vae' and so he always

  days a level of tension that corresponds to the absolute value like

  the effective value of the voltage Va as applied to the

  of the electric motor 20, so that Va '= A1 x Var - Vati = A1 x Va (1) On the other hand, the signal Vm obtained by passing the positive terminal potential of the resistor 52 in the filter pass bottom 62 has a voltage level, such that:

25728 16

  Vm = Ra x Im (2) where Ra is the resistance value of the resistor 52, and Im is

  the average value as the effective value of the armature current Io.

  On the other hand, there is a relation such that: Va = Im x Rm + Vs (3), where Rm is the internal resistance of the electric motor 20, and Vs is an induction voltage as the counter-electromotive force of the motor 20 The signal Vm is amplified in the amplifier 63, to be generated as a signal Vm ', so that: Vm' = A2 x Vm (4),

  o A2 is an amplification coefficient.

  The signals Va 'and Vm' are sent to the plus and minus input terminals of the subtracter 61, to obtain the feedback signal Vf, such that: Vf = A3 x (Va '- Vm') (5),

  o A3 is an amplification coefficient.

  By substituting the expression (l) in -expression (3), we obtain: Va '= A1 x-I mx Rm + Vsl I (6) Rm is always of positive value, and Im x Rm and Vs are also of same sign when the armature current Io is sent in each direction of conduction. Therefore, expression (6) can be written as: Va '= A1 x Rm x | Iml + Al x iVsl (6')

  Substituting expression (4) in expression (2), we obtain

  holds: Vam '= A2 x Ra x Im (7) By substituting the expressions (6') and (7) in the expression (5), we obtain: Vf = A3 x (A1 x Rm x IImi + A1 x IVsJ A2 x Ra x Im) (8) Since the positive terminal voltage of the resistor 52 has a constant sign, the current value Im in the expressions (2)

  and (7) at the base of the signal Vm 'to be determined by means of the resistance

  this 52 always has a positive value.

  As a consequence, the value of Im of the term A2 x Ra x Im in

  expression (8) is always positive.

  Moreover, in this embodiment, the coefficient

  A1 amplification factor of the subtractors 57, 58 and the amplification coefficient A2 of the amplifier 63 are determined so that: AL x Rm = A2 x Ra Thus, by eliminating the terms (A1 x Rm x / Im1) and (A2x Ra x Im) in Expression (8), we obtain the expression: Vf = A3 x A1 x IVs | (9)

  As has been described, the voltage Vs is the inductive voltage.

  as counter-electromotive force of the electric motor 20, while the counter-electromotive force is proportional to the rotational speed N of the motor 20 and therefore: Vs = Ke x N (10), where N is the rotational speed expressed in rpm taking into account the direction of rotation, and Ke is a voltage induction coefficient

in terms of volts per rpm.

  By substituting the expression (10) in the expression (9), we obtain: ## EQU1 ##

o k = A3 x A1 x Ke.

  As is apparent from the expression (11), the output signal

  Vf of the subtracter 61 has a voltage proportional to the value

  solute of the rotation speed N of the motor = electrical 20, that is to say

  say, the number of turns per unit time of it.

  In the above description, the voltage signal VP at

  send to the input terminal plus of the differential amplifier 41

  is given as a signal representing the relative angular difference

  peripherally dP as a phase shift between the input and output shafts 1,4, and further, as described, the voltage Va to be applied to the electric motor 20 corresponds to the output signal VP1 of the amplifier 41, while the signal VP1 is obtained by negatively returning the voltage signal Vf in the voltage signal VP, the signal Vf being in correspondence with the speed

25728 16

  of rotation N of the electric motor 20, so that the signal Va

  has a voltage substantially proportional to that of the signal VP.

  As a result, the electric motor 20 is driven to rotate at a speed N (rpm) proportional to the phase shift dP between the input and output shafts 1,4. It will be understood that the circuit elements 56, 59, 57, 58, 60, 51, 62, 63 and 61 are arranged to cooperate together to send back

  the signal Vf as a function of the rotation speed N of the electric motor

  20 to stabilize its rotation as a function of the signal.

VP.

  As will be understood from the foregoing description,

  in the electromagnetic servo device according to this

  embodiment, the number of revolutions or the rotation speed

  N of the electric motor 20 is adjusted according to the difference

  Relative angular difference as a phase shift between the input and output shafts 1,4, so that the electric motor 20 can be controlled in a favorable speed according to the actions of the shafts 1,4. For example, with a couple of direction applied gently

  by the steering wheel to the input shaft 1, when the difference

  this relative angular dP between the input and output shafts 1,4, is produced at a relatively small angle, the electric motor

  is then excited to rotate at relatively

  weakly, which provides an auxiliary torque to the output shaft 4 via the reduction gears 32,

  33, the output shaft being thus forced to move at short

  its relatively weak to a position where the input shaft 1

is turned.

  On the other hand, when a steering torque is applied abruptly to the input shaft 1, when the angular difference

  relative dP between trees 1.4 is produced at a relative angle

  large, the electric motor 20 is then driven to rotate at relatively high rotational speeds, the output shaft

  4 being forced to move at relatively high speeds

  to a position where the input shaft 1 is rotated. When the output shaft 4 approaches the rotational position of the input shaft 1, the relative angular difference dP between the shafts

  1.4 nevertheless becomes lower, which correspondingly reduces

  the speed of rotation N of the electric motor 20.

  Due to this speed setting of the electric motor 20, the output shaft 4 is rotated gently following the rotation of the input shaft 1, without producing any delay thereto. In addition, in connection with the rotation of the tree of

  output 4 which closely follows the input shaft 1, the rotational speed

  N of the electric motor 20 is automatically changed by being progressively reduced when the relative angular difference dP decreases, which prevents the output shaft 4 from being effectively

  turned too fast due to the moment of inertia of the rotor 26 of the

20.

  In other words, when the input shaft 1 is rotated 1.5, the electric motor 20 and thus the output shaft 4 are successfully set so that the output shaft is driven to be followed by the output shaft. near the rotation of the input shaft 1, a

  stably, with a favorable sensitivity to it.

  In addition, in the rotation of the output shaft 4 which closely follows the rotation of the input shaft 1, the rotational speed N of the electric motor 20 is adjusted, advantageously using the relative angular difference dP, way to vary it depending on the size of the load imposed as a couple on

  the output shaft 4. For example, when the input shaft 1 is

  to turn quickly so as to have an angular difference

  relatively large relative to the output shaft 4, if the load imposed on the output shaft 4 is smaller than expected, the rotation speed N of the DC electric motor 20 then tends to be diverted to its region of high speeds, due to its own operating characteristics, in

  exceeding a point provided by the VP signal. However, when the

  N has become larger, even by a small amount, the feedback signal Vf then has a correspondingly increased voltage as will be seen from the expression (11), so that by the function fulfilled by the circuit elements 44, 43, 42, and 49, the voltage Va in the electric motor 20 is reduced, which prevents an increase in the speed N. In other words, the output shaft 4 is actually controlled to be driven in order to turn, closely following the input shaft i in a stable manner, having a favorable sensitivity thereto and, furthermore, taking sufficient account of

  the load torque imposed on the output shaft 4.

  Although what is currently considered to be the preferred embodiment of the invention has been described,

  note that the present invention can be realized under

  10 specific forms without departing from the spirit or characteristics

  essential ticks of it. This exemplary embodiment should therefore be considered in all respects by way of illustration and

  non-limiting. The scope of the invention is indicated by the claims

  following statements rather than the previous description.

Claims (5)

  1. Improvement to an electronic servocontrol device   tromagnet (200) including an input shaft (1), a   an output (4), an electric motor (20) for producing an auxiliary torque   to the output shaft (4), a detecting means (13) for detecting a phase shift (dP) between the input shaft (1) and the output shaft (4), and a circuit control unit (100) arranged for   providing, for the motor (20), a control signal (Va) for   and thus an armature current (Io) in a regulated quantity, in one direction   controlled conduction thereof, as a function of a detection signal.   Vr, V) from the detection means, characterized in that it is constituted by the control circuit (100) in which   the control signal (Va) for the motor (20) is provided to re-   set a rotation speed (N) of the motor (20) according to the detection signal (Vr, V2).   2. electromagnetic servocontrol device according to claim 1, characterized in that the control circuit (100) is arranged to provide the control signal (Va) for the engine   (20), to make the rotational speed (N) of the motor (20) proportional to   to the amount of phase difference (dP) between the input shaft (1) and the output shaft (4).   Electromagnetic servocontrol device according to Claim 2, characterized in that the control circuit (100)   includes a first circuit (71) for producing a quantity signal.   phase shift (VP) and a phase shift direction signal (VR, VL)   showing the amount and direction of the phase shift (dP), as a function of the detection signal (Vr, V) from the detection means (13), a second circuit (72) arranged to receive the phase shift amount signal (VP) and the phase shift direction signal (VR, VL) and for   produce, depending on these, the control signal (Va) at   to the motor (20), and the second circuit (72) being arranged to produce the control signal (Va), so that the control signal (Va) has a polarity of its voltage determined from the sense signal of phase shift (VR, VL) and a level of its voltage set to be proportional to a signal value of the amount of phase shift (VP). 2572816 '   4. Electromagnetic servo device   according to claim 3, characterized in that the cir-   control furnace (100) further comprises the elements (56, 59, 57, 58, 60, 52, 62, 63, 61, 41) provided for the second circuit (72) and arranged to return to the   signal of phase shift quantity (PV) a signal (VF)   presenting the absolute value of the rotational speed (N) of the engine (20).   5. Electromagnetic servo device   characterized in that it - further comprises a speed reducing mechanism (32, 33) for transmitting a motor torque of the motor (20) to the output shaft (4), in a manner reducing speed. SR 3094 JP / DC